When preparing adhesives for packaging in aerosol canisters or containers, solvent-based adhesives have been employed almost exclusively because of their ease of use, solvency in the propellants, wide range of tackiness, quick drying rates and economy. These adhesives are prepared by dissolving solid polymers, plasticizing oils, tackifying and reinforcing resins and preservatives in volatile organic solvents such as hexane, pentane, toluene, xylene, methylene chloride, 1,1,1,trichloroethane, naphtha and methyl ethyl ketone. These solvent-based adhesives have a number of undesirable characteristics such as being health hazards, their flammability, and they release large amounts of harmful volatile organic compounds into the atmosphere.
The product of the present invention is an adhesive which is non-flammable, does not constitute a health hazard, and whose only volatile ingredient is water. When packaged along with a non-flammable, non-polluting propellant in pressurized canisters, a useful, sprayable adhesive is obtained which has all of the desirable attributes and none of the undesirable attributes of prior art spray or aerosol adhesives.
Common adhesives intended for use in building construction and with flooring and floorcovering materials, such as, for example, wood plank, parquet, artificial turf, boat or other marine carpets, indoor carpet, rubber flooring, cove base molding etc., are water-based emulsions based upon either acrylic or styrene butadiene (SBR) latex. Acrylic-based formulas, due to their expense and low bond strength, are generally reserved for use only when necessary for a pressure-sensitive applications, for resistance to plasticizers in pure vinyl backings or for resistance to sunlight in outdoor applications. SBR-based adhesives for use in building construction, flooring and floorcovering are, by far, the predominant type and require the addition of a tackifier to develop bond strength and a proper modulus.
The traditional means of producing an adhesive of this type is to emulsify the SBR latex to form a latex emulsion. Additional constituent components, such as, for example, process oil, tackifying resins, mineral fillers, etc., are also emulsified. The latex emulsion is then added to the constituent component emulsion under various heat and pressure conditions to form the adhesives.
The adhesives produced by the traditional method have several associated disadvantages, such as, for example, poor water resistance, slow drying, high volatile organic compound content and limitations on the final solids content of the adhesive. These disadvantages are generally due to the use of emulsifiers and thickeners in forming the adhesive. Emulsifiers and thickeners are generally water-soluble compounds that remain in the dried adhesive and tend to adversely affect the water resistance and durability of the resultant adhesive bond. Water soluble compounds also tend to retard the drying rate of the water-based adhesive. Moreover, using a method in which all constituent components are emulsified prior to mixing severely limits the solids content of the final product. It is particularly desirable to produce adhesives having a high solids content due to their superior bonding and drying characteristics.
It is also desirable to eliminate the presence of volatile organic compounds (VOC) generally present in traditional adhesives of the type described above. VOCs are generally used to dissolve the tackifying resins which are incorporated into the adhesive to develop bond strength and an appropriate modulus. Since these resins are generally solid at room temperature, they must be liquified in order to be incorporated into the constituent component emulsion. This is usually done by dissolving the resin in an organic solvent carrier. Organic solvents are usually quite volatile and may have adverse effects on the environment due to their contribution to air pollution. VOCs also degrade the performance of the resulting adhesive by slowing down curing time, swelling and weakening the rubber component, shortening the life of the applied product and raising the level of emulsifier required for emulsion stability, which, in turn, further degrades the adhesive. The use of organic solvents to produce adhesives, in some cases, also requires the use of expensive solvent recovery equipment required by government regulation and has the further disadvantage of exposing employees to the potentially harmful organic solvents.
VOCs are also incorporated into latex-based adhesives to improve their freeze resistance. Because traditionally formulated SBR-based adhesives have a high water content, they usually have poor freeze resistance. Manufacturers have sought to overcome the poor freeze resistance by introducing VOCs such as methanol and glycol to lower the freezing point of SBR-based adhesives. However, the addition of these VOCs results in many of the same disadvantages set forth above. In order to overcome the disadvantages associated with the use of VOCs for improved freeze resistance, some manufacturers have attempted to substitute non-volatile compounds such as sorbitol to improve freeze resistance. While freeze resistance may be improved in this manner, the water resistance of adhesive using non-volatile water-soluble compounds such as sorbitol is adversely affected.
It is desirable, in many applications involving adhering floor coverings to a substrate, to apply the adhesive quickly over large surface areas. The use of a propellant to spray the adhesive would provide the ability to do so, however, prior to the present invention, sprayable adhesives were generally required to have low solids contents in order to provide a sufficiently low viscosity, and were mostly solvent-based adhesives. Further, the propellants used heretofore have generally been either flammable, or pollutants, or both. Thus, such products have not met with a substantial degree of success commercially, and/or have sufficient drawbacks that a need continues to exists for an adhesive application system in which a water-based, high solids adhesive is packaged in a spray canister with anon-flammable, non-polluting propellant.
It is an important object of this invention to provide an adhesive having a high solids content.
It is a further object of the present invention to provide an adhesive having improved bond strength and stability.
It is another object of the present invention to provide an adhesive containing little or no volatile organic compounds.
It is yet another object of the present invention to provide an adhesive that produces a bond having improved water resistance and durability.
It is still another object of the present invention to provide an adhesive having improved drying rates and faster application characteristics over prior art water-based adhesives.
Another object of the present invention is to provide a freeze-stable SBR-based adhesive having no VOCs and improved water resistance.
It is further an object of this invention to provide an adhesive with a low viscosity suitable for spray application.
It is also a objective of this invention to provide a water based adhesive which is stable under pressure in metal canisters.
Another object of this invention is to yield a water based adhesive which is not coagulated or harmed by the propellant which ejects it from the canister.
It is a further important object of the present invention to provide an adhesive that will be stable through the large pressure drop experienced when released from a pressurized canister, and that will not foul or clog the nozzle.
It is a further object of the present invention to provide a high-solids, solvent-free, water-based adhesive for use in an adhesive application system in which the adhesive is pressurized and sprayed from a canister by a non-flammable, non-polluting propellant.
It is a further object of the present invention to provide an adhesive having the advantages described above and which will not be a health hazard.
Another object of the present method is to provide a non-flammable adhesive.
A further object of the invention is to provide an adhesive which will adhere carpet to floors.
It is also an object of the present invention to provide an adhesive which will adhere athletic surfaces and artificial grass to substrates such as concrete and wood.
It is a further object of the present invention to provide an adhesive useful for gluing textile fabrics, carpets and plastic films to fiberglass reinforced plastics, wood, metal, leather, rubber polyvinylchloride and polyurethane components.
It is an additional important object of the present invention to provide an aerosolized adhesive composition for use in aerosol spray applications.